Google's trends reports that New York City leads the world in Google searches for the word "ballet." Reports are in terms of # of searches for the topic divided by total # of searches (a/k/a normalized data). San Francisco is second.
Trends is tricky to apply to ballet companies. For instance American Ballet Theater searches peak around the time of Met Seasons, with New Yorkers leading the search parade. But American Ballet Theatre (just flipping last two letters) is more tied to national events (e.g., PBS telecasts, White House performances) and Los Angeles leads in interest. ABT prompts a search for a drug company with that ticker symbol. New York City Ballet peaks around Nutcracker season.
http://www.google.com/trends?q=ballet